Edison Standard D model phonograph
The Edison Standard D model phonograph dates from around 1908 and has a clockwork spring-powered motor. It has been fitted with a recorder head that can play back two-minute cylinders.
Recording on this equipment is a purely mechanical process, with no electricity involved. The performer sings down a metal horn and the energy of that sound is concentrated onto a thin circular mica disc in the recorder head. The vibrations of the disc move a thin glass rod which cuts the spiral groove in the cylinder.
The distance of the performer from the horn is critical; the performer has to be able to hear a reverberant echo coming back out of the horn for there to be enough mechanical energy to cut the groove.